The present invention relates to novel regenerative sorbents for removal of sulfur containing hydrocarbons (organic sulfur compounds) from hydrocarbon liquid streams and, more particularly, a Cu/La zeolite sorbent for removing organosulfur compounds from diesel fuel.
Many approaches have been applied to the control of sulfur in fuel feedstreams. These approaches vary with the fuel and the type of sulfur compounds involved. In the case of coal, there are three options where sulfur removal may be applied. When coal is burned directly for power, for example, sulfur exists as oxides and is removed from the gas effluent from the combustor. When coal is gasified, sulfur exists as hydrogen sulfide and may be removed by conventional methods from the gaseous effluent. A third option being explored is to remove the sulfur during gasification of the coal, a process which requires coal pretreatment. The latter process offers the advantage of treating the sulfur problem in a less hostile environment and where the sulfur compounds are more concentrated, reducing the complexity of the removal process.
In the case of liquid fuels, the first two cleanup process options described above are commonly applied. In the area of the third option, hydrodesulfurization of the fuel, for example, is a commercial process where the fuel is treated at high temperatures with high pressures of hydrogen to produce hydrogen sulfide. The hydrogen sulfide is subsequently removed in a relatively low temperature process with either a solid material like zinc oxide, or a liquid. Regeneration is a highly desirable, if not required, property of the hydrogen sulfide sorbent. When the sulfur compounds are removed prior to the gasification or combustion process, the task is more economically viable and technically simpler. Although hydrodesulfurization is commonly used commercially, it is not a simple process due to the incorporation of a catalyst bed, a sorbent bed, and a recycle of pressurized hydrogen feed. At the present time there is no commercially available material which would remove the sulfur compounds directly from the common liquid fuels and be capable of regeneration. Such a process would eliminate the need for pressurizing and recycling hydrogen as well as eliminating the catalyst bed.
One option to removing H.sub.2 S from the gasifier gas streams is to remove the sulfur from the liquid feedstock prior to the gasification process. In the case of liquid hydrocarbon feedstocks, such as Diesel fuel or fuel oil, this requires the selective removal of the sulfur-containing hydrocarbons (organosulfur compounds) from the feedstock. This can be accomplished, conceivably, when the feedstock is in either the liquid or gaseous state. The desired goal would be to remove all organosulfur compounds, eliminating the need for any down stream scrubbing devices. However, the removal of one-half or more of the organosulfur compounds would greatly reduce the duty requirements and/or size of the downstream scrubber. This would greatly enhance possibility for providing clean output gas streams of a quality suitable for feeding to fuel cells or gas turbine power plants.
Efforts addressing the problem of sulfur removal from liquid, hydrocarbon, feedstock have been suggested but no solutions have been found. The problem has been one of capturing the sulfur compounds to a high degree under such partitioning effects that occur in a dynamic situation, and of understanding how to selectively remove them from a liquid on a continuous basis, as compared to a batch process.